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Difference Between Delayed Sleep Phase (DSP) & Delayed Sleep Phase Syndrome (DSPS)

An informative article, but it falls into the usual "daywalker" trap that DSPS is caused by poor sleep hygiene and bad habits. It can be, but for a delayed sleep phase to be properly described a "syndrome", a degree of inability to be "normal" should be there. I'm not an expert, but my understanding is that recent studies have shown a genetic propensity to delayed sleep phase in sufferers.

Kevin's Thoughts

Your point is well taken and thank you for sharing it. One thing I want to make clear from the very start in response to your first sentence is that at no time do I make the distinction that "bad" habits cause a delayed sleep phase. We all operate under the influence of different lifestyles and preferences when it comes to sleep time, and in no way did I suggest in the article that a delayed sleep phase is in any way inherently bad. In fact, I believe that quite a large number of people are better suited to a delayed sleep phase than a "normal" sleep phase. There's been many a discovery made in the unorthodox hours of the night by an alert mind operating upon a delayed sleep phase.

As to your second point regarding the use of the word "syndrome" in DSPS, your point is very well received. Different people certainly have different propensities to adjusting their biological clock, and as a result delayed sleep phases take on various levels of severity. So the question is when is it appropriate to use the word syndrome when describing a DSP? You suggest the inability to advance phase (shift the biological clock back up) must be present, but let me offer you a slightly different view based on the writings and teachings of Dr. William Dement, regarded as the foremost authority, and indeed the father of, sleep medicine.

In his Stanford Sleep Book, Dr. Dement implies that a "delayed sleep phase" becomes "delayed sleep phase syndrome" when the dip in biological clock alerting needed to sleep is delayed beyond the desired time to be asleep.

Under this definition then, someone who wishes to go to bed at 11 PM, say, in order to awaken with sufficient sleep by 7 AM for work, but cannot fall asleep consistently until 2 AM due to a delayed sleep phase actually would qualify as having the "syndrome" ending attached to the name. Utilizing the right strategies (such as bright light therapy) in the right manner they could shift their biological clock, but as long as they stayed in a delayed phase with the desire to go to bed before they are able to, the condition would be considered a syndrome under this definition.

This hypothetical schedule would ultimately lead the individual to experience the range of other symptoms involved with the sleep deprivation that would accumulate. And indeed, the definition of the word "syndrome" itself calls specifically for a group of symptoms that together are characteristic of a condition, rather than an inability to rid oneself of it. And since the symptoms themselves are going to exist in just about anyone who desires an earlier sleep time, regardless of their inherent ability to shift their biological clocks while in a delayed sleep phase, it is more their desire rather than their ability to advance phase that qualifies the word "syndrome".

All this is not to discount the significance of the difficulty many people experience in shifting their biological clocks to schedules they would rather have. People do adjust their biological clocks with vastly different levels of ease. Dr. Dement also writes that in DSPS "there is a theoretical implication that the ability of the circadian system to phase advance may be sluggish or actually abnormal" but in most cases of the syndrome it is more likely that the delayed phase is maintained by a combination of the person's behavior and their body's late-night alerting, rather than an inherent disability. This kind of sheds more of a gray light over the distinction between DSPS and DSP.

What do you think of this argument? I'd be curious to know, because it is by no means an absolute or end-all answer, as I imagine there may be various points of view on this distinction even among professionals within the sleep circle. If I find out more about varying views of experts I'll be sure to update this page.


Comments for Difference Between Delayed Sleep Phase (DSP) & Delayed Sleep Phase Syndrome (DSPS)

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Mar 13, 2011
Comment on lifestyle and DSPS
by: Brian M

I my case it has nothing to do with lifestyle. I struggled through decades of "normal" work hours complete with good sleep hygiene and only felt rested after several "days" of sleep. It is a biological issue (in my experience) and until there is a good treatment for it, I have to live with it.

Oh and I worked outside for decades with full sunlight and it did not help, nor did the exercise and fresh air!

Dec 20, 2012
It's not habbits that effect my sleep. NEW
by: Anonymous

I can tell you that with me it is not a choice what so ever to go to sleep at 9am and wake up at 7pm. It sucks and I have tried everything except a light box but I have very sensitive eyes so I doubt that would work for me. I really wish they would do more studies and research to find a cure for this... it has destroyed my life.

Mar 10, 2013
Glad to see a positive take on DSP vs DSPS NEW
by: Anonymous

I am always skeptical of labeling people who prefer and excel while following a certain schedule of sleep as having a disorder when it differs from the norm. This article, with its noted differentiation between DSP and DSPS goes to the heart of this issue and seems to make a clear distinction between what constitutes a "disease" diagnosis versus a mis-diagnosis - an "ease" rather than a "disease". I personally thrive on sleeping from about 5 or 6 am till waking in the mid-afternoon. Thankfully I am self-employed in a field that gels perfectly with this sleep/wake cycle. It infuriates me to be labeled as disordered when friends of mine who like to wake at the crack of dawn (or even earlier) are considered normal, even though their sleep/wake style actually interferes with their chosen profession. What is normal about waking at 430 am and going to sleep at 930 pm when it clearly conflicts with a work and personal schedule that would benefit from a different sleep/wake time schedule. Many people live their lives this unproductive way and are never diagnosed with I might facetiously but quite accurately call an "early awakening sleep disorder" (EASD). While sleep research can determine common characteristics of so called "normal" sleep behavior, even proving a scientific basis for it, there are always exceptions. I think it is a very common mistake to use pejorative terms for things that differ from the norm. I would be very curious to hear that people who live in a geological location of the world that annually experiences months of darkness are disordered when their sleep/wake cycle differed from the accepted "wake at 6 am, go to sleep at 10 pm" norm. Would we label someone who lived on the moon, or Mars, or some other celestial body that rotates at something other than a 24-hour schedule, as having a sleep disorder because it varied from the earthly norm? While I understand that there may be clear scientific reasons for concluding that sleep schedules that fail to correspond to circadian rhythms corresponding to natural biological processes related to light and darkness, we must be cautious about labeling any deviation as a disease. Evolution must be perforce fraught with examples of species exhibiting behaviors that were temporarily anachronistic, only to be proven with time to be adaptive. A sleep cycle that may be labeled as a disorder may be just as likely to be a natural behavior, given the particular genetic makeup of an individual and his environment. After all, I've heard that sleep researchers often work night shifts. :-)

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